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R. T. BELL March 15, 1960 FRACTIONAL CONDENSATION METHOD OF METHANETHIOL RECOVERY FROM REACTION MIXTURES THEREOF 4 Sheets-Sheet 1 Original Filed Dec. 7. 1951 March 15, 1960 R, T, BELL Re. 24,796

FRACTIONAL CONDENSATION METHOD' OF METHANETHIOL RECOVERY FROM REACTION MIXTURES THEREOF Original Filed Dec. '7. 1951 4 Sheets-Sheet 2 RICHMOND 7.' BELL March 15, 1960 R T BELL Re. 24,796

FRACTIONAL CONDENSA'II'IO'N METHOD OF METHANETHIOL RECOVERY FROM REACTIUN MIXTURES THEREOF ATTORNEY March 15, 1960 R. T. BELL Re. 24,796

FRACTIONAL CONDENSATION METHOD OF METHANETHIOL RECOVERY FROM REACTION MIXTURESTHEREOF Original Filed Dec. 7, 1951 'he'tlB-Sheet 4 coa/.ER 54 600i. El? 4/ STO/MGE TANK FIG. 4

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R/GHMO/VD 7.' BE L L ATT RNE Y th BY FRACTIONAL CONDENSATION METHOD OF METHANETI-IIOL RECOVERY FROM REAC- TION MIXTURES THEREOF Richmond T. Bell, Grayslake, Ill., assignor to The Pure Oil Company, Chicago, Ill., a corporation of Ohio i 13 Claims. (Cl. 260-609) Matter enclosed in heavy brackets .appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to the production of methanethiol from methanol andhydrogen sulfide by means of an efficient, catalytic, continuous process, preferably operated under superatmospheric pressure. It is specifically concerned with a continuous process for preparing methanethiol by reacting methanol and hydrogen sulfide in the presence ot a metallic oxide catalyst and processing the reaction eiliuent in a product recovery section to recover methanethiol and Z-thiapropane. l This application is a continuation of U.S. patent application Serial No. 260,353, filed December 7, 1951, now abandoned.

Although the batchwise preparation of methanethol by reacting methanol and hydrogen sulfide in the presence of asuitable metallic oxide catalyst is well-known, heretofore no comercial process for continuously manufacturing methanethiol has been available. Previous efforts which `were carried out incidental to other work were crudely executed and results therefrom were inconclusive and misleading. The processing methods employed were so inadequate that the production of substantial quantities of l-thiapropane was not even discovered, muchless recovered, and as nearly as can be determined material balances were only about 50%. methanethiol and 2-thiapropane as articles of commerce as organic intermediates, particularly for the production of methionine, sulfoniurn compounds, and methyl sulfonates and sulfates, as well as other uses, has made the availability of a commercial process `for manufacturing these compositions desirable. Accordingly, it is an object of this invention to provide a practical and eicient continuous process for manufacturing met-hanethiol, recovering and separating 2-thiapropane, and recovering unconverted methanol, and if desired, hydrogen sulfide.

It is a further object to provide a process for manufac- 'turing methanethiol and -thiapropane which is operated under pressures suicient to permit eiiluent condensations, separations, and recoveries to be made without resorting to coolant temperatures lower than those ordi# narily available in waters ffor industrial use.

Av schematic diagram of a continuous process for producing methanethiol is shown in Figures 1 and 2. Modifications of the recovery section of `this process are illustrated diagrammat-ically by Figures 3 and 4.

The preparation of mercaptans or organicthiols may be carried out by various methods. Perhaps the` most `simple is the direct method of passing the vapors of an alcohol admixed with hydrogen sulfide over suitable metallic oxide catalysts such as thoria at elevated temperatures. In this method there is induced a metathetical interchange of the hydroxyl group of the a1- nf I ICC

eohol with the sulfhydryl group of the hydrogen sultde in accordance with the following reaction:

The etlorts of the prior art workers to produce mercaptans by this method have been confined to improvements in the preparation or reaction phase of the process. The problems involved in the continuity of processing and product recovery aspects of mercaptan preparation were unrecognized because the small volume and type of product obtained in the laboratory experiments described in support of their methods did not make them cognizant of the problems that existed, particularly in connection with the preparation of low molecular weight mercaptans' and alkyl suldes such as methanethiol and 2thiapropane. These compounds are obviously more volatile than the higher molecular weight products and present product recovery diiiiculties, not extant in handling thevhigher molecular Weight products, which must be overcome in providing an etlicient, continuous process for the produc- The importance of catalyst by means of a suitable valve manifold system tion of methanethiol and Z-thiapropane. It has been found that these processing difliculties can be overcome by employing the manipulative process described by this invention.

When methanol and hydrogen sulfide are reacted to form methanethiol there is produced a reaction etliuent consisting essentially of methanethiol, 2-thiapropane, water, and unconverted methanol andhydrogen sulfide.

Referring to the accompanying drawing, it isseen that.`

the preferred general basis for the .recovery and separation of the products and uncovered reactants issuing from the reactor is fractional condensation and stabilization.

This sequential operation is shown in Figures 1 and In carrying out this process the charge to the process heater 10 is comprised of recycle materials together with such fresh methanol and hydrogen suliide as may be necessary. The fresh methanol is charged by means of line 11 and fresh hydrogen sulde is charged through line 12, connected to suitable sources of supply. For example, the hydrogen suliide may be obtained as a byproduct from petroleum reiining operations, carbon disuliide production which employs hydrocarbon gases and elemental sulfur as reactants, or from any other available means. The recycled reactants obtained, as hereinafter described, from the product recovery section of the process may be reintroduced into the process heater 10, by means of lines 13 and 14, if desired. The hydrogen sulfide is heated separately from the methanol in one section of the heater, and enters the stream of methanol, early in lits heating, being vaporized and heated-in the other section of the heater. In this way, thorough mixing and vuniform heating of the reaction mixture is secured. The temperature at which the gaseous reaction mixture from the process heater enters the reaction chamber depends on the conditions of space velocity, catalyst activity, pressure, reactant ratio, temperature, etc., under which the reaction is to be carried out. Under ordinary conditions, it is usually somewhat lower than the catalyst temperature desired, Within about 20 F. of said temperature. The pre-heated reactants are passed to the reactors 15 by means of line 16.

Alternate catalyst chambers 15 permit uninterrupted operation. When the activity of the catalyst in the on-` stream reactor declines, the reactants can be turnedinto the other chamber containing regenerated or fresh while a mixture of super-heated steam and air is ad-l mitted to the spent catalyst to burn off carbonaceous and sulfurous deposits and regenerate `its activity. This gaseous regeneration mixture is supplied by an auxiliary 3 system consisting of a steam superheater 17 and corn.- pressor 18. Steam from a suitable source is introduced into the superheater 17 by means of line 19. Air 1s supplied by line 20 tio compressor 118'. The super-heated steam and compressed air are admixed and supplied to the regeneration system through line 21. In the instance where a supported thoria catalyst is employed, the cornposition of the air-steam mixture, its rate of flow, and its temperature should be such that the .temperature of the catalyst during regeneration docs .not exceed arnaximum of 850 F. Exposing the catalyst to higher temperatu'res" risks permanent, substantial impairment kof its activity. The lowest temperature at 'which the regeneration can be carried out satisfactorily is the most desirable operating temperature. vWhile Figure l shows the use of avtxed bed type of operation, the reaction phase of thepprocess may also ybe alternatively carried out in the r moving bed type operation employing either a granular so as to leave a desired, small quantity of Water in the recycle methanol. As another means. whereby water `may be introduced into the reaction zone water can be added directly to the fresh methanol charged. s 1

Thorium oxide, supported or unsupported, is one of the suitable catalysts for the reaction, but other `metallic oxide catalysts which are effective are the oxides of zirconium, titanium, uranium, tungsten, molybdenum, chromium, vanadium, manganese, zinc, cadmium, and aluminum. Although all the oxides of these metals are effective for the purposes of this invention, in cases where several oxides of a given metal exist, intermediate oxides between the lowest and highest oxide, whether Well-defined oxides, consistent molar compounds, or mixtures of higher and lower oxides are preferred.

While the metallic oxides may be used per se, it is mined by moist litmus. Thereafter the temperature was raised to 756 F. as rapidly as possible without causing local overheating or excessive temperature gradients, and was maintained at 750 F. until exit gases were completely free of acidic constituents. After removal from this] reactor, the catalyst was screened to separate any es.

As another example, the same quantities of materials were employed but with water as a solvent for the thorium nitrate tetrahydrate instead of methanol. Also, a somev` what finer average mesh pumice was used, viz., that retained on 16 mesh screen. In general, the fines from a thoria-pumice catalyst prepared in this way `were between 1 and 2% by weight of the' combined Weight of the thoria, as calculated from the initial `weight of thorium nitrate, and the initial weight of purified pumice. v.The thori in the lines can `be easily reclaimed as nitrate. Taking handling losses into account, and considering fines as thoria, the pumice/thoria mol ratio in both finishedv catalysts was about 13/1. Areprcsentative molecular` weight of 67.7 for purified pumice was used. Before use, these catalysts were conditioned by pre-treatment with methanol vapor in accordance with U.S. Patent 2,592,646.

The cflluent vapor mixture from the catalyst reaction chamber' 15, consisting principally of water, methanol, Z-thiapropane, methanethiol and hydrogen sulfide, `passes by means, of line 22 through heat exchangers 23 and 24 and a cooler 25, whereby a part of the two highest-.boiling components, water and methanol, is condensed and collected in accumulator 26. Liquid methanol-water, :saturated With the three vapor components under ambient con@ ditions, is pumped through line 27 to the demethanolizer and dehydrator column 28, and crude 2thiapropaneme thaethiol-hydrogen sulfide vapor mixture containing methanol and water vapor is taken from the top of the accumulator 26 by a` compressor 29 and passed through line 30 to a confluent point Where the streams are admixed and pass into the demethanolizer and dehydrator column 28 through line 31.

The demethanolizer and dehydrator column 28, which is a fractional distillation apparatus, functions as a stabilizer-fractionator to strip methanol and water free of k, thiapropano-methanethiol-hydrogen sulfide vapor, and .to

usually preferable to support them on a carrier such as since it Vhas va minor degree of catalytic activity itself underv the ordinary `range of reaction conditions. Thoria is preferred for the more active component of the catalyst, but when indicated by better availability or economics oxides of the other metals listed may be substituted. Zirconia -and titania are other oxides which are also favored.

The activity of a supported thoria catalyst is dependent upon the'method and care used in its preparation, particularly with respect to the temperatures and heating schedules employed. Very effective catalysts With pumice/ thoria mol ratios between 10/1 and 30/1 may be prepared from thorium nitrate and pumice purified by extraction with hydrochloric acid until free of iron oxides and other metallic oxides and compounds extractable with hydrochloric acid. For example, a '25% by weight solution of 1`l5 parts of thorium nitrate tctrahydrate in 345 parts of methanol was poured into 169 parts of purified pumice,and'themixture was continuously stirred at 120 to'140 F. until the methanol was evaporated. Further drying was carried out ata constant temperature of 230 F. over aperiod' of 1'5 hours.. r

The pumice' impregnated with thorium nitrate was then decomposed in a specialjractor tube. Measurements of temperature weremade regularly at various points in the y Smooth .anduniform heating was provided. VThe catalyst was slowly brought to 525 F.V over a period of condense all ymethanol and water from this( vapor. The liquid methanol-water is recovered as bottoms from this tower and transferredby line 32 toanother fractional distillation tower 33. The rein the methanol-water frac,- tion is separated into a methanol overhead product and a water residue. The methanol thus recovered passes to a storage tank 34 from which it is pumped back to the process heater 1.0 through exchanger 24 as Vrecycle charge stock. The separated water flows to a waste disposal system. The overhead vapor from column 23 consisting essentially of 2-thiapropane, methanethiol and hydrogen sulde passes through a cooler 35 to an accumulator 36, whereby a major part of the 2rthiapropane is condensed.

, The liquid and vapor therefrom are passed through line 6 hours, wit'hra current of dry air Ypassing through, after which time exit gases were` only' slightly acid as deteris conducted to va storage tank 39 as a ley-product of the process when the primary purpose of operation is to produce methanethiol. jective iny operating this process it is often desirable to introduce a small amount of Zathiapropane with the charge in order to retard thiapropane formation and improve overall operation and efliciency for production of methanethiol. Thus the flow diagram in Figure 2-shows a line d() `connectingy the 2-thiap'ropane drawolflinet' the When such purpose is the main obrecycle methanol line 13. The overhead vapor from column 38 passes through a cooler 41 to condense most of the methanethiol, and thence to an accumulator 42. Liquid methanethiol from this accumulator 42, saturated with hydrogen sulfide under ambient conditions, is pumped through line 43 to column 44. Hydrogen sulfide containing methanethiol vapor is taken from the top of the accumulator 42 by a compressor 45 and passed through line 46 to join the stream of liquid methanethiol, and the combination then porceeds through line 47 into column 44.

In column 44, which in this embodiment of the invention is another fractional distillation apparatus, methanethiol is stripped free of hydrogen sulfide, and any methanethiol is condensed fromthe hydrogen sulfide. The hydrogen sulfide passes overhead through ia cooler 48 and accumulator 49. If desired the hydrogen sulfide may be recycled by means of line 50 through a compressor 5I and exchanger 23 to the process heater 10 as recycle charge. Liquid methanethiol from the bottom of column 44 passes through line 52 to column 53' for rectification. In column 53 the pure methanethiol is taken overhead through a cooler 54 to an accumulator 55. Liquid methanethiol from the accumulator is pumped through line 56 to storage facility 57. i

Alternatively, the process can be carried out as shown in Figure 3. In this variation the overhead from column 28 enters an absorption tower 58 wherein the feed is contacted with an absorbent such as white oil or kerosene. In order to assure the absence of unsaturated hydrocarbons and a very low sulfur content, highly refined hydrocarbon products such as these are preferred. However, 'other petroleum products of similar boiling ranges, such as light lubricating oil base stocks, gas oil, light fuel oils,

or heavy naphthas are suitable providing tbe contents of unsaturates and sulfur are low. The methanethiol andv2- thiapropane are absorbed, and the unabsorbed hydrogen sulfide passes overhead as residue off gas and may be returned through line 50 to the process heater 10 as recycle charge, if desired. The fat absorbent rich with methanethiol and 2-thiapropane is pumped from the bottom ofthe absorber 58 through a heater 59 to a stripping tower 60 where the rich absorbent is denuded of [mathanethiol] methanethiol and 2-thiapropane which pass overhead through a cooler 61 to an accumulator 62. The lean absorbent is pumped from the stripper 60 through cooler [64] 63 where it is again contacted with afeed consisting of the overhead from column 28. Hydrogen sulfide, saturated with methanethiol and 2thiapropane under ambient conditions within the accumulator 62, is led from the top of the stripper accumulator 62 by means of line 65 back to join the stream of overhead entering the absorber from column 28. The liquid mixture of methanethiol and 2-thiapropane is pumped from the bottom of the accumulator 62 to column 38, functioning principally as a fractionator, where 2thiapropane is drawn from the bottom to storage and methanethiol passes overhead Ythrough a cooler 41 to accumulator 42. However, in this variation of the process line 46' from the top of accumulator 42 runs back to join line 65 leading from the ytop of the stripper accumulator, instead of being trans ferred to column 44 as shown in Figure 2. The compressor 45 is then located between the point where the two accumulator vapor lines 46' and 65 join and the pointv where this common line meets line 37 carrying overhead Vfrom column 28 to the absorber 58. In this variation of the process column 44 is eliminated and liquid methanethiol is pumped from the bottom of accumulator 42 to column 53 where it is purified and thereafter passed to storage. Also, the absorber is preferably operated at pressures between 30 and 90 pounds per square inch absolute and the stripper at pressures about to l0 per square inch less than that in the absorber.

i As a further embodiment of this invention the process canvbe carried out as shown Aby Figure 4. In this embodiment the overhead from column 28 enters an absorption tower 66 wherein the feed is contacted with an absorbing medium. Suitable absorbents include aqueous and glycol solutions of alkylol amines such as mono, di, and triethanolamine, alkacid solutions such as those of sodium alanine, potassium diethyl glycine, and sodium phenolate, and solutions of alkali metal salts such as those of tripotassium phosphate, potassium carbonate, and sodium carbonate. Aqueous solutions of monoor di-ethanolamine are preferred absorption media. The hydrogen sulde is absorbed and thiol-thiapropane passes overhead through a cooler 67 to an accumulator 68. A vapor line 69 from the top of this accumulator runs back to join line 37 entering the absorber 66 from column 28. Liquid thiolthiapropane is pumped from the bottom of the absorber accumulator 68 to column 38. thiapropane mixture is [process] processed in accordance with the variation described above and diagrammatically in Figure 3.

Absorbent rich with hydrogen sulfide is pumped from the bottom of the absorber 66 through a heater to the stripper, passes thro-ugh a cooler 72 and an accumulator 73, and may be returned via line 50 to the process heater 10 as a recycle charge, if desired. Any liquid condensate in the stripper accumulator 73 is pumped from the bottom of the accumulator 73 back to the line 37 carrying` overhead from column 28 to the absorber 66. Lean absorbent from the bottom of the stripper 71 passes through a cooler 74 to an accumulator 75 from whence it is recycled to the top of the absorption tower 66.

In general, operation according to the combination of steps represented by Figure l, under pressure sufficiently high to permit use of coolants at temperatures commonly available, is preferred. Also, with either of the embodiments represented by Figures 2 and 3 operation under said pressures is preferred. In the modification represented by Figure 4, operation of the absorber and stripper under the lowest pressures practical in relation to the rest of the recovery system is preferred. When ordinarily available coolants such as industrial water having a temperature between 60 and 100 F. are used, notable economies and more eicient operation is possible. The use of superatmospheric operating pressures permits the use of such coolants.

However, still more flexibility for adaptation to local conditions or changing Veconomics is achieved by additional alternatives. The variations represented by Figures l, 2, 3 and 4 may be conducted under substantially atmospheric pressure. If this procedure is employed refrigeration of the coolants is required; or, the reaction section up to the cooler preceding the initial receiver may be operated at substantially -atmospheric pressure with the recovery and l separation section including and following said cooler maintained under the aforementioned superatmospheric pressures.

Under usual ranges of conditions, conversions, and coolant temperatures, pressures ranging up to about 600 pounds per square inch absolute sulice, and pressures in excess of about 1000 pounds per square inch absolute seldom will be required. This invention is not so limited, however, and if the process is so conducted that stabilizer reboiler temperatures and/or stabilizer partial condenser temperatures are unusually high, pressures up to about 1500 pounds per square inch absolute can be imposed as required.

A specific example of the process conducted according to the combination of steps represented in Figures l and 2 is as follows: With a reactor (catalyst center) temperature of 788 F., a space velocity of 657, a hydrogen sulfide to methanol mol ratio of 1.004 to l, a methanol to water mol ratio of to l, atmospheric pressure, and a pumicesupported thoria catalyst, a total methanol conversion amounting to 54.5 of the maximum possible is achieved. Methanol conversion to methanethiol is 46.7% of the maximum possible and conversion to Z-thiapropane is Thereafter the thiol-r 7.8%, an excellent conversion ratio (percent to CHaSH/ percent to (CH3)2S) of about 6. The yield of methanethiol per pass per 100 pounds of methanol charge is 7.0.1 pounds and the yield of 2-thiapro`pane is 7.6 pounds. The material balance is 99.8% by weight.

When the reactor effluent is cooled by the' fheat eri-y changers, cooler, and accumulator lto about 275 F., and the kettle temperature of column 28 is vmaintained at about 275 F., the pressure required for operation of the col umn' to produce liquid bottoms consisting essentially fof only methanol and water isapproximately 185 to 90 pounds per square inch absolute. v

The mol fraction of methanol in the bottoms is about 0.43 and that of Water 0.57. f

The methanol and Water bottoms from column 28 are transferred to column 33 where, with the kettle temperature at about 275 F., a pressure of about 45 to 50 pounds per square inch absolute is required for operation to produce water botto-ms vvith a minimum `content of methanol. With the temperature of the methanol vapor in the condenser for column 33 at about 200 F., the pressure required on the condenser is about 40 4to- 45 pounds per square inch absolute. However, column 33 and yits condenser may be operated at [subtsantially] substantially atmospheric pressure when the kettle temperature is about 210 F., and that of the vapor distillate Y inthe condenser is 150 F.

With the vapor distillate from column '28 (approximate mol fraction composition: hydrogen sulfide=0.5l0, methanethiol=0.452, 2-thiapropane=0;038) a't `a tempcrature of about 80 F. in the condenser, Vthe pressure required on 'the condenser is about 85 to 90 pounds per square inch absolute. The approximate mol fraction composition of the reflux is: hydrogen suliide=0.2l7, methanethiol=0.620, and 2-thiapropane=0.162.

Proceeding to column 33, with the kettle temperature at about 215 F., a-pressure of about 85 to 90 poundsyper square inch absolute is required for operation to produce the desired bottoms, essentially only 2-thapropane.

,With the vapor distillate from column 3S (mol fractions: hydrogen suliide=0.53, methanethiol=0.47) at a temperature of about 70 F. in the condenser, the pres- 'sure required on the condenser is about 85 'to 90 pounds per square inch absolute, and the approximate mol fractionpzreuxncomposition is hydrogen sulde='0.25, I'nethi-inethiol:0.75.v l

In column 44, for operation to produce bottmnsv consisting substantially of methanethiol only, a pressure of about 27Q`to 275 pounds Aper square inch absolute is ret quired with the ykettle temperature at'about 235 F.

yWith the hydrogen sulfide vapor distillate from column itat a temperature of about 70 F. in the condenser,'the pressure on the condenser is about 265 to 2701 pounds per square inch absolute. v y

Y High purity methanethiol is produced -by rectification of the bottoms from column 44 in column "53 Where, in order vto produce pure methanethiol vapor distillate and bottoms comprising only higher boiling impurities, a presi vWith the methanethiol vapor distillate 'at a temperature of about 70 F. in the condenser, the pressure on the condenser is about 25 to 30 pounds per square inch absolute. At atmospheric pressure, refrigeration of the coolants used in the recovery and separation section is required,

inch absolute. Thus by the use of suitable superatmosf pheric pressures, refrigeration of coolants is eliminated or substantiaily reduced, separations are more precise and efficient, and the ratio of yields to equipment size is substantilly increased, these advantages being obtained With-4 l,out decrease in methanethiol conversion .or substantial change in the ratio of methanethiol conversion: pane conversion.

The foregoing specifiic examples of the instant invention are intended to be only illustrative. Othermanipulative techniques embodying this invention will be obvious to those skilled in the art. Such equivalent systems are Within the scope of this invention. Y

What is claimed is: Y

l. yIn a continuous process for the production of meth anethiol wherein methanol and hydrogen sulfide are reacted at an elevated temperature in a reaction zone in the presence or" a catalyst capable `of splitting oi water *toV produce a reaction .eilluent consisting essentially of water, methanol, 2-`thiapropane, methanethiol, and hydrogen sulfide, the improvement which comprises fractionally condensing said etiuent in a product recovery process maintained at a suitable superatmospheric pressure not in excess of about 1500 p.s.i.a. to obviate the need for mechanical refrigeration in said recovery process and permit the use of cooling water at a temperature of about -100" 1F. for cooling and frictionally condensing the several constituentsof the reaction eluent, said process comprising introducing Said effluent into a rst fractional condensation zone, fractionally condensing said eluent at a suitable elevated pressure with cooling water at a temperature o Vabout 6`tl100 F. to produce-a irst liquid phase consisting essentially of water and methanol,

2-thiaprovand a rst gaseous phase consisting essentially of 2* thiapropane, methanethiol and hydrogen sulfide and stabilizing said liquid and gaseous phases to produce a first, liquid, `bottoms fraction consisting essentially of Water and methanol, and a iirstfgaseous, overhead-fraction consisting essentially of 2-thiapropane, methanethiol, and

hydrogen sulfide; introducing said rst overhead frac# tion into a second fractional condensation zone, fractionally condensing said fraction at a suitable elevated pressure with cooling water at a temperature of` about 60-l0( F. to produce a second liquid phase consisting essentially of 2-'thiapropane and a second gaseous phase consisting essentially or methanethiol, and hydrogen sull fide and stabilizing said liquid and gaseous phases to produce a second, liquid, bottoms fraction consisting essentially of 2-thiap'ropane and a secon-d, gaseous overhead fraction consisting essentially of methanethiol and hydrogen sulfide; and introducing said second overhead fraction into a third fractional condensation zone, Yfractionally condensing said fraction at a suitable elevated pressure with cooling water at a temperature of 602100 F. to produce a third liquid phase consisting essentially of methanethiol, and a third gaseous phase consisting esentially of hydrogen suliide and stabilizing said phases to produce a third, liquid, bottoms fraction consisting essentially of methanethiol, and third overhead product consisting essentially of hydrogen sulfide. y

2. In a process in accordance with claim l the steps of fractionally distilling said tirst, liquid,y bottoms `frat:-

tiony consisting essentially of methanol and Water,v `r`e A covering the methanol and recycling said methanol to said lreaction zone. I

3. In a continuous `process for lthe production (of methanethol wherein methanol and hydrogen sulde are reacted at an elevated temperature in a reaction plone in the presence of a. catalyst capable of splitting oifwatger to produce a reaction eluent'consistingfessentially of water, methanol`,'2 thapropane, methanethiol, :and -hydrogen sulide, Athe improvement which comprises frac'- tionaliy condensing said eiliuent in a product recovery process maintained at La Vsuitable-superatmospheric pres .9 sure not in excess of about 60G-1G00 p.s.i.a. to obviate the need for mechanical refrigeration in said recovery process and permit the use of coolingwater at a temperature of about 60-l00f F. for coolingA end fractionally condensing the several constit-uents ofy the reaction eflluent, said process comprising cooling said reaction efliuent at a suitable elevated pressure Wit-h cooling water at a temperature of 6l00 F., to produce a first liquid phase consisting essentially of Water and methanol, and a first gaseous phase consisting essentially of Z-thiapropane, rnethanethiol and hydrogen sulfide, admixing said liquid phase and said gas phase to produce a first, gas-liquid admixture, stabilizing and fractionating said admixture to produce a first, liquid, bottoms fraction consisting essentially of water and methanol, and a first, gaseous, overhead fraction consisting essentially of Z-thiapropane, mcthanethiol, and hydrogen sulfide; cooling said first overhead fraction at a suitable elevated pressure with cooling Water at a temperature of about 60-l00 F. to produce a second liquid phase consisting essentially of 2-thiapropane and a second gaseous phase consisting essentially of methanethiol, and hydrogen sulfide, admiring said liquid phase and said gas phase to produce a second, gas-liquid admixture, stabilizing and fractionating said admixture to p-roduce a second, liquid, bottoms fraction consisting essentially of Z-thiapropane and a second, gaseous overhead fraction consisting essentially of methanethiol and hydrogen sulfide; cooling said second overhead fraction at a suitable elevated pressure with cooling Water at a temperature of 60-100 F. to produce a third liquid phase consisting essentially of methanethiol, and a third gaseous phase consisting essentially of hydrogen sulfide, admixing said liquid phase and said gas phase to produce a third, gasliquid admixture, stabilizing and fractionating said' admixture to produce a third, liquid, bottoms fraction consisting essentially of -methanethioh and third overhead product consisting essentially of hydrogen sulfide.

4. In a process in accordance with claim 3 the step of rectifying said third bottoms fraction to [recovery] recover substantially pure methanethiol.

5. In a process in accordance with claim 3 the steps of fractionally distilling said first, liquid, bottoms fraction consisting essentially of methanol and Water recovering the methanol and recycling said methane to said reaction zone.

6. In a continuous process for the -production of methanethiol wherein methanol and hydrogen sulfide are reacted at an elevated temperature in a raction zone in the presence of a catalyst capable of splitting ofi water to produce a reaction efliuent consisting essentially of Water, methanol, 2-thiapropane, methanethiol, and hydrogen sulfide, the improvement which comprises fractionally condensing said eiuent in a product recovery process maintained at a suitable superat-rnospheric pressure not in excess of about 60G-1000 p.s.i.a. to obviate the need for mechanical refrigeration in said recovery process and permit the use of cooling water at a temperature of about 60-l00 F. for cooling and fractionally condensing the several constituents of the reaction eiuent, said process comprising cooling said reaction efiiuent to a temperature of about 275 F. at a suitable elevated pressure with cooling water at a temperature of 60-100 F., to produce a first liquid phase consisting essentially of water and methanol, and a first gaseous phase consisting essentially of Z-thiapropane, methanethiol and hydrogen sulfide, admixing said liquid phase and said gas phase to produce a first, gas-liquid admixture stabilizing and fractionating said admixture at a temperature of about 275 F. and a pressure of 80-90 p.s.i.a. to produce a first, liquid, bottoms fraction consisting essentially of yWater and methanol, and a first, gaseous, overhead fraction consisting essentially of Z-thiapropane,

.Tmethane'thioL and hydrogen sulfide; cooling' first overhead fraction to a temperaturen! about 8B" Ff at a' pressure of about 85-90 p.s.i.a. with cooling`water`at liquid phaseconsisting essentially OlQZ-thi'apr'opane and a lsecond' gaseous phase 4consisting essentially Vof Imethane"- thiol, and hydrogen sulfide, adr'nixingv said liqnidi'p'hase and said gas phase to produce 'asecond,` gas-liquidi admixture, stabilizing and fractionating said admixture at a temperature of about 215 F. and a pressure of about -90 p.s.i.a. to produce a second, liquid, bottoms fraction consisting essentially of 2thiopropane and a second, gaseous overhead fraction consisting essentially of methanethiol and hydrogen sulfide; cooling said second overhead fraction to a temperature of 70 F. at a pressure of 85-90 p.s.i.a. to produce a third liquid phase consisting essentially of methanethiol, anda third gaseous phase consisting essentially of hydrogen sulfide, admixing said liquid phase and said gas phase to produce a third, gas-liquid admixture, stabilizing and fractionating said admixture at a temperature of 235 F. and a pressure of about 270-275 p.s.i.a. to produce a third, liquid, bottoms fraction consisting essentially of methanethiol, and third overhead product consisting essentially of hydrogen sulfide. i l

7. In a continuous process for the production of methonethiol by the reaction of methanol and hydrogen sulfide at elevated temperatures in a reaction zone in dontact with a solid catalyst capable of splitting off water to produce u reaction effluent containing water, methanethiol, 2-thiapropone and lhydrogen sulfide, the improvement which domprises cooling said reaction effluent to a temperature at which at least a portion of said eluem is condensed by means of cooling water at a temperature of about 60100 F., fractionat'ing the cooled ejluent without mechanical refrigeration, at a pressure suiciently high to permit condensation of the product fractions` using a cooling fluid at a temperature of 60-I00 F.,

into an aqueous methanol fracton,` a methanethiol' fraction and a hydrogen sulfide fraction, said methanethiol and hydrogen sulfide fractions being .separated front each other by introducing aV mixture' thereof to a stripping zone and therein removing hydrogen sulfide as an loverhedd fraction, heating and recycling said hydrogen sulfide to the reaction zoneinlet, and fractionating the liquid from the bottom of sai/id stripping zone to remove higher boiling impurities from said methanethiol.

8. Process in accordance with claini7 in which the pressure is below 1500 pounds per square i'nch absolute.

9. Pnocess in accordance with claim 7 in which th cooled eluent from the reaction zone is fractionated to separate a thiapropane fraction, the of'queous methanol fraction is charged to a separate fractiortuting zone wherein methanol is separated as an overhead fraction from water, the water is eliminated frlorn lthe system and the methanol is recycled to the reaction zone after admixture with hydrogen sulfide. i

10. Process in accordance with claim 7 in which the reaction zone is maintained at a higher pressure than the pressure at which the coo-led eluent'isfractionnted.

11. Process in accordance with cliiim 7 in which the catalyst contains as an essential constituent, activated alumina. y

12. Process in acclordance with claim 7 in which said methanethiol arnd hydrogen sulfide fractions are `separated from each other by contacting the mixture thereof in an absorption zone with an absorption liquid preferentially absorbent flor methanethiol, withdrawing unabsorbed hydrogen sulfide fromy sdd one as the hydrogen sulfide fraction, stripping and condensing the methanethiol from the absorption liquid and fractionating the rne'tha'ethiol to remo-ve higher boiling constituents.y

13. Process in accordance with claim 7 in which said lmethanethiol and hydrogen sulfide fractions arefsepardted References Cited in the le of this patent ufrom each'other by contacling the mxiure thereof in an or the original patent `labsorption zone with an absorption liquid preferentially UNITED STATES PATENTS `absorben# for hydrogen sulfide', withdrawing and condensing unabsorbed methanethiol from said zone, Istripping 5 l 953019 Bergstrom Mar' 29' 1910 hydrogen sulfide from the absorption liquid as the hy- 2009554 Lacomble July 30 1935 2 147 400 Clark et al Feb. 14 1939 .drogen sulfide frzctxon, and fractzonatzng the methanefhxol 2'6 67 51 5 Y B h l 5 to rmrovezhgher boiling constituents. eac et a Ian' 26 19 4 

